A damping force generator for a hydraulic shock absorber as disclosed in Japanese Examined Utility Model Application Publication No. H02-47790 (Patent Document 1) is structured as follows: A vehicle body side inner tube is slidably inserted in a wheel side outer tube. A hollow pipe provided with a bulkhead portion, which is in slidable contact with the inner periphery of the inner tube, is installed upright on the bottom of the outer tube. An oil chamber, in which a piston provided within the inner periphery of the inner tube advances and retracts, is provided around the hollow pipe. The oil chamber is comparted by the piston into an upper oil chamber located above the piston and a lower oil chamber located below the piston. The interior of the hollow tube is defined as an oil reservoir chamber that reaches the upper part of the inner tube, and an air chamber is located above the oil reservoir chamber. An annular interspace chamber is provided between the outer tube and the inner tube, located between a slide guide secured to the inner periphery of the outer tube and a slide guide secured to the outer periphery of the inner tube. Holes communicating this annular interspace chamber with the oil chamber around the hollow pipe are formed in the inner tube. A damping force generator is provided between the upper oil chamber and the lower oil chamber around the hollow pipe that allows the oil to flow into the upper oil chamber in the compression stroke and creates a passage resistance to the oil flowing out of the upper oil chamber in the extension stroke.
The damping force generator as described above is designed so that the outer periphery of the damping valve is secured to the piston on the inner tube side and an extension-stroke damping force is generated as a high pressure in the upper oil chamber which pushes open the damping valve by bending (causing a deflection in) the inner periphery thereof.